Tuner mechanisms in car radios are generally compatible with manual and automatic tuning operations. A tuning operation is effected by manually rotating a manual tuning knob or by pushing a pushbutton to which a desired broadcasting station is previously reserved. Both the rotation of the manual turning knob and the displacement of the pushbutton are finally transmitted to a tuning circuit element for varying the frequency selection.
FIG. 1 is a schematic view of main components relating to tuning operation of one of such prior art pushbutton tuners. To effect manual tuning operation, the manual tuning knob 1 is manually rotated to displace a memory slide plate 3 transversely. The displacement of the memory slide 3 is transmitted to a change lever 5 via a connection member 4. The change lever 5 then changes a constant of a tuning circuit element 6 such as an inductance element, for example. To effect automatic tuning operation, a desired frequency is preset to a pushbutton 7 by said manual tuning operation so that the memory slide plate 3 always moves to a determined position corresponding to the desired frequency when the pushbutton 7 is pushed. As well known, a lever 8 fixed to the pushbutton 7 carries a cam-shaped frequency setting plate 11 which has a pin 9 and is pivotal about the point 10. The frequency setting plate 11 is sandwiched by a pair of lock plates 12a and 12b. If the pushbutton 7 is pushed into the tuner toward the memory slide plate 3, the pin 9 contacts and is guided by a wave-shaped edge 13 of the memory slide plate 3. When the pin 9 falls in one of the ravines of the wave-shaped edge 13, the frequency setting plate 11 is forcibly seized by the lock plates 12a and 12b and locked there unrotatably. Thereafter, by merely pushing the pushbutton 7, the pin 9 associated to the pushbutton 7 and now fixed in its angular position pushes the wave-shaped edge 13 of the memory slide plate 3 and displaces it to the position corresponding to the preset frequency whereat the pin 9 falls into the ravine. The displacement of the memory slide plate 3 is transmitted to the tuning circuit element 6 via the connection member 4 to change its value and select the reserved frequency.
The connection member 4 used in prior art tuners for transmitting the displacement of the memory slide plate 3 to the tuning circuit element 6 upon operation of the tuning knob 1 or of the pushbutton 7 bridges a pin 14A projecting from the memory slide plate 3 and a pin 14B projecting from a frame 15 of the radio. Additionally, a spring 16 is parallelly provided above the connection member 4 to maintain reliable linkage between the memory slide plate 3 and the change lever 5.
With this structure, however, a considerably large distance D is required between the memory slide plate 3 and the frame 15 for assembly of the connection member 4 and the spring 16. Additionally, since the connection member 4 and the spring 16 must be assembled in a limited space around or just under the tuning circuit element 6 which is already assembled, the assembling work is extremely difficult.
In the prior art tuner, an intermediary member such as the change lever 5 for transmitting the displacement of the memory slide plate 3 to the tuning circuit element 6 also occupies a space and disturbs reduction of size of the tuner because the change lever 5 horizontally juts out from the tuning circuit element 6.